Edexcel Core 3 - 21st June 2016 AM

Jw. Someone posted this:
http://www.thestudentroom.co.uk/attachment.php?attachmentid=553966&d=1466461962

for d) would you look at when cos does 2 repeats and then find t for that, assuming you let theta = pi(t)/5?

I remember this was our mock paper in Year 13. It seems your reasoning is correct.

Reply 1081

username1529975

13

Original post by 1 8 13 20 42

I remember this was our mock paper in Year 13. It seems your reasoning is correct.

does that mean u do 4pi + alpha = pi(t)/5 ?

Reply 1082

Mathskid137

1

Am I right in thinking only a 'one to one' has an inverse function whereas 'many to one' and 'one to many' need restrictions to have an inverse function (like x>0)?

Reply 1083

username1529975

13

Original post by Mathskid137

Am I right in thinking only a 'one to one' has an inverse function whereas 'many to one' and 'one to many' need restrictions to have an inverse function (like x>0)?

whenever a question says 'why doesnt it have an inverse' write 'many-to-one'

Reply 1084

math42

20

Original post by Tow

does that mean u do 4pi + alpha = pi(t)/5 ?

Well, how I would think on it is like this. Two revolutions is 4pi radians, right? Hence you want to find t such that (pi*t)/5 = 4pi and this indeed yields the correct t value

Reply 1085

username1529975

13

Original post by 1 8 13 20 42

Well, how I would think on it is like this. Two revolutions is 4pi radians, right? Hence you want to find t such that (pi*t)/5 = 4pi and this indeed yields the correct t value

that's what I was thinking, hm... not sure why i put alpha in the equation... this was a half guess though. Didn't think about it enough. So I'm guessing the answer would be found through 4pi = pi(t)/5?

Reply 1086

tammymxx

2

really hoping they serve us some nice trig questions

Reply 1087

ryandaniels2015

11

Please help anyone

Original post by ryandaniels2015

thanks but does this not mean u have to show cast or graph?

Reply 1088

username1529975

13

Original post by 1 8 13 20 42

Well, how I would think on it is like this. Two revolutions is 4pi radians, right? Hence you want to find t such that (pi*t)/5 = 4pi and this indeed yields the correct t value

Also... if you don't mind, could you explain Q3c please?

http://qualifications.pearson.com/content/dam/pdf/A%20Level/Mathematics/2013/Exam%20materials/6665_01R_que_20130613.pdf

Not sure how/when the equation only has one solution.

edit: Nvm khaleesi answered!

(edited 7 years ago)

Reply 1089

khaleesi98

7

Original post by Tow

I've just found it, it's the June 2013R paper, Q3c.

Paper:
http://qualifications.pearson.com/content/dam/pdf/A%20Level/Mathematics/2013/Exam%20materials/6665_01R_que_20130613.pdf

MS:
http://qualifications.pearson.com/content/dam/pdf/A%20Level/Mathematics/2013/Exam%20materials/6665_01R_msc_20130815.pdf

Right the graph of cosx in that range has two solutions for every y value between 0 & 1, but only one solution for y=-1 and for y=1.
So set the cos part of the equation = to -1...
R(-1) = k, so k = -R
...and = to 1...
R(1) = k, so k = R

Or look at this...
https://07a69ccf283966549a9350d1a66951a7bc96e2dc.googledrive.com/host/0B1ZiqBksUHNYZ0JQM1NRcmdHdXM/June%202013%20(R)%20MA%20-%20C3%20Edexcel.pdf

Reply 1090

username1529975

13

Original post by khaleesi98

Right the graph of cosx in that range has two solutions for every y value between 0 & 1, but only one solution for y=-1 and for y=1.
So set the cos part of the equation = to -1...
R(-1) = k, so k = -R
...and = to 1...
R(1) = k, so k = R

Or look at this...
https://07a69ccf283966549a9350d1a66951a7bc96e2dc.googledrive.com/host/0B1ZiqBksUHNYZ0JQM1NRcmdHdXM/June%202013%20(R)%20MA%20-%20C3%20Edexcel.pdf

Ooooooooh yeah gotcha. Thanks! :smile:

Goodluck for tomorrow!

Reply 1091

math42

20

Original post by Tow

that's what I was thinking, hm... not sure why i put alpha in the equation... this was a half guess though. Didn't think about it enough. So I'm guessing the answer would be found through 4pi = pi(t)/5?

Yah you literally just rearrange for t there.

Original post by Tow

Also... if you don't mind, could you explain Q3c please?http://qualifications.pearson.com/content/dam/pdf/A%20Level/Mathematics/2013/Exam%20materials/6665_01R_que_20130613.pdfNot sure how/when the equation only has one solution.

Man these are the ugliest and most boring questions around, but generally speaking you naturally use the Rcos(x-alpha) form derived, and here sketching a graph over the range 0 </=x < 360 degrees might be prudent

Reply 1092

sakuraton

12

Goodnight guys and good luck!!

Reply 1093

selenmer

10

Original post by 1 8 13 20 42

Well, how I would think on it is like this. Two revolutions is 4pi radians, right? Hence you want to find t such that (pi*t)/5 = 4pi and this indeed yields the correct t value

Sorry why do you make pit/5 = 4pi. What has the pit/5 got to do with It all

Reply 1094

5824

1

Do you guys know when to use f '(x) to show a function is increasing or decreasing, and when to use f ''(x) ??

Reply 1095

xdaryaxx

Original post by Zacken

If anybody needs any urgent help, feel free to tag me and I'll respond as soon as I can.

hi I just wanted to ask do you know which formules and Identities I need to learn of by heart for c3

Reply 1096

Simple Harmonic

2

Original post by 5824

Do you guys know when to use f '(x) to show a function is increasing or decreasing, and when to use f ''(x) ??

First derivative gives the gradient of the graph. If it yields a positive value at a particular x value, the function is increasing at that point, and vice-versa.

The second derivative is mainly used to find the nature of stationary points (minima or maxima). A positive second derivative value (with a first derivative value of 0) indicates a minima and vice-versa.

Reply 1097

MaggieXUE

1

guys！！whwn is your exam time （uk time ）？？？mineis 8am

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Reply 1098

undercxver

18

I just completed the C3 June 2011 paper and got 80 something percent and for a C3 June 2015 paper I got 48/75, which I believe is 2 marks off an A since that paper was ridiculously hard. That's the highest I've got in the papers I completed today. :lol: